The purpose of this thread is to give everyone cool experiment ideas. Disclaimer: If you die from these experiments it's not my fault!

I think my absolute favorite, so far, would be the non-Newtonian liquid.

Take cornflour (maybe one cup?) and some water (start with half a cup and only add more if you need to, I'm not sure about the quantities ). Mix them together. If you have the right relations between the two, you'll get a bizarre liquid - if you punch it or poke it quickly, it acts as a solid. However, slow actions allow it to act as a liquid. You can pick up a chunk of it very quickly (as a solid it's a bit powdery) and then have it ooze off your hand. Very entertaining.

I also enjoy squeezing citrus peels on open flames (makes small sparks because of the oil in it, IIRC). Another interesting one is a demonstration of low and high pressure - pour some water into a shallow plate, put something in it that you can stick matches into (a piece of potato or something). Stick to matches in it, light them up and quickly cover it with a glass. The glass needs to touch the water. The fire extinguishes the oxygen and overall you get low pressure inside the glass which causes it to suck in water to equalize it.

Another cool one is putting a bar of soap in the microwave. You need to clean it a bit afterwards, though...

What about your favorite experiments? BTW, did anyone try to mentos and diet coke one yet?

Zohar wrote: Another interesting one is a demonstration of low and high pressure - pour some water into a shallow plate, put something in it that you can stick matches into (a piece of potato or something). Stick to matches in it, light them up and quickly cover it with a glass. The glass needs to touch the water. The fire extinguishes the oxygen and overall you get low pressure inside the glass which causes it to suck in water to equalize it.

this is one of those school science experiments that works for a completely different reason than that normally given. the change in pressure is due to the hot air above the match/candle cooling, it has nothing to so with 'using up oxygen'.

I have two, but they aren't exactly "home" experiments, but are good if you have access to the required materials...

1. vacuum cannon
Basically, you get a long pvc pipe that is just barely big enough to fit a ping pong ball through and fit a valve near one end. Then you put a ping pong ball in one end and seal off the ends with clear packing tape or similar material (needs to be air tight). Next you need a pretty good vacuum pump (why this isn't exactly a "home" experiment) to pull almost all of the air out of the tube. Now, you simply puncture the tape on the end of the tube where the ping pong ball is sitting and let atmospheric pressure do the rest. I've used this to fire the ping pong ball through a soda can! I've seen it dozens of times and it still blows my mind.

2. soap explosion
This is a pretty simple states of matter experiment, but since it requires liquid nitrogen and most people don't have access to that, it's not really a "home" experiment either. Take a good sized bucket, at least a couple of gallons and fill it about an inch deep with water and put a good amount of dish soap in there (dawn, etc). Next you just need about a liter or two of LN2 and you want to throw the LN2 into the soapy water as quickly as possible for best results. I've been able to hit the ceiling in low ceilinged elementary school gyms with the soap bubble plume from this.

A note on safety: I doubt the ping pong ball has enough mass to seriously injure a person, but if you're close, it would probably leave a welt, also the cannon is kinda loud, so covering your ears may be smart. For the soap explosion, it's harder to hurt yourself with LN2 than most people think, but it is still possible. For safety, you should wear eye protection and cryo gloves for the soap explosion. Also, make sure that you don't miss the bucket and pour all the LN2 on your foot....if you do, it's probably not smart to leave the liquid nitrogen soaked clothing on your body.

demonstrating that water is not very compressible (not exactly one for kids):

take a glass bottle and fill it with water so there is no air at all in it. hit the top of the bottle/water with the flesh part of your thumb/palm. with enough force you should be able to blow the bottom of the bottle off like this. (i take no responsibility for any injuries sustained from broken glass this way.)

edit:

yes lots of things to do with liquid nitrogen. you can pour it over you hand quite safely (make sure you have no rings on or anything which could trap the liquid though). and there is the flash freezing things like flowers or fruit.

put chocolate or cheese or something in a microwave with the rotating plate removed. cook for a few seconds until the chocolate/cheese is melted in some places. this gives you the wavelength of your microwaves. the frequency should be 2.5 GHz (from water absorption spectra, or teh internets) the speed of light is then the frequency times the wavelength

Zohar wrote: Another interesting one is a demonstration of low and high pressure - pour some water into a shallow plate, put something in it that you can stick matches into (a piece of potato or something). Stick to matches in it, light them up and quickly cover it with a glass. The glass needs to touch the water. The fire extinguishes the oxygen and overall you get low pressure inside the glass which causes it to suck in water to equalize it.

this is one of those school science experiments that works for a completely different reason than that normally given. the change in pressure is due to the hot air above the match/candle cooling, it has nothing to so with 'using up oxygen'.

How come? Won't the air take up the same volume before starting the experiment and after letting it cool down to room temperature?

the air is initially very hot (easily 1000K just above the flame) this means it will be much less dense than normal air. when you put the jar over it you stop it being able to mix with normal density air so you have a hot gas filling a volume. now as that gas cools it will lose volume (see ideal gas law). there will be some O2 -> h2O which will also reduce the volume when the H2O condenses (otherwise the combined CO2 and H2O would occupy more volume than the O2, which is hopefully obvious as we have just burnt a load of candle and put it in the air i.e. the is H and C in it now). its also worth noting that the experiment won't use up all the O2 in the air either, so you end up with quite a complicated mix of reasons why the final volume is what it is.

When a match burns, it doesn't use up air; it uses up oxygen, but it replaces it with equal amounts of carbon dioxide. This is because wood is mainly composed of carbohydrates (primarily cellulose), and carbohydrates burn according to the chemical reaction CmH2nOn + mO2 -> mCO2+nH2O. So combustion doesn't actually reduce the amount of molecules of gas present (and in fact increases the number, as the water produced is in gaseous form). However, it also produces quite a bit of heat, so when you cover the matches with the glass, you are trapping warm air inside. As the warm air cools, the pressure decreases (since with a fixed number of gas molecules in a fixed volume, the ratio between temperature and pressure is constant), and this is what causes the lower pressure in the glass.

I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

2) Melt a depression in one of the blocks of dry ice (a small torch for soldering plumbing works nicely).

3) Place Mg turnings in the depression and ignite them with a flame (use the same torch as in step 2).

4) Quickly place the second block on top of the first, sealing the burning Mg inside a carbon dioxide tomb.

5) Enjoy the light display (best in a dark area).

6) When the reaction is complete, remove the top block and examine the material inside.

You should find a grey-white mottled ball. This is MgO, which formed by stealing oxygen from the dry ice (thermodynamics strike again!). If you crack open the ball (best to wait until it has cooled) you will find it is full of black material. This is pure carbon, produced when the dry ice donated oxygen to the Mg.

IMPORTANT: Be sure the blocks of dry ice fit together smoothly or the burning Mg will draw in oxygen from the atmosphere and you won't produce the beautifully pure carbon powder.

"Whenever you find yourself on the side of the majority, it is time to reform (or pause and reflect)."-- Mark Twain"There is not more dedicated criminal than a group of children."--addams

Here's the deal:
1. Get a glass of water.
2. Pour a drop or two of milk into it - not much!
3. Give it a stir so it's well-mixed.
4. Turn off the light.
5. Shine a flashlight through the glass.
6. Observe.

A white-colored LED flashlight works best. You should notice a distinctly redder beam exiting the glass and a distinctly blue light emanating in all directions from the glass.

Conglaturations, you're seeing the same effect that gives us a blue sky and red sunset!

evilbeanfiend wrote:put chocolate or cheese or something in a microwave with the rotating plate removed. cook for a few seconds until the chocolate/cheese is melted in some places.

To here:

evilbeanfiend wrote:this gives you the wavelength of your microwaves. the frequency should be 2.5 GHz (from water absorption spectra, or teh internets) the speed of light is then the frequency times the wavelength

My personal favorite: liquid nitrogen bomb. Bonder and I were in the same group that did these things, so I'm surprised he didn't mention it. Procedure:

Obtain a quantity of liquid nitrogen, a sturdy soft-drink bottle (preferably 2-litre), and a ditch or something (for shrapnel protection). Fill the bottle as much as you can with nitrogen; wipe any frost off the neck, cap it extra-tight, and toss it into the ditch (or far away from people, at least). Walk casually in the other direction, and try not to laugh too maniacally when the blast comes.

Memorable incidents include the time we didn't think our 2-litre was actually going to explode; a quiet hissing noise was followed, about 15 seconds after it became inaudible, by the most impressive bang we ever got. For public demonstration, we usually put the bottle into a steel bucket (partly filled with water, for heat conduction), placed into a plastic garbage bin with the lid on. As a result, our campus physics building's roof has at least one trash can lid stranded on it.

evilbeanfiend wrote:put chocolate or cheese or something in a microwave with the rotating plate removed. cook for a few seconds until the chocolate/cheese is melted in some places.

To here:

evilbeanfiend wrote:this gives you the wavelength of your microwaves. the frequency should be 2.5 GHz (from water absorption spectra, or teh internets) the speed of light is then the frequency times the wavelength

???

The microwave produces "standing waves". What's important to know, for our purpose, is that there are points in the microwave where the radiation intensity is zero all the time. So when you put something inside without the rotating plate, the points of zero radiation don't heat up at all and thus don't melt. On the other hand, there are points which experience the maximum of radiation available so they melt a lot.

The distance between the points (either between minimums or between maximums) is exactly the wavelength of the radiation in the microwave.

This is why you use a rotating plate - so no part of the food stays cold. Of course, this never works...

BTW, I was hoping for some more experiments you can actually do with homemade materials, not ones requiring liquid nitro, dry ice etc. Although they're cool, they require quite a bit more work that I was thinking.

Zohar wrote:The microwave produces "standing waves"....The distance between the points (either between minimums or between maximums) is exactly the wavelength of the radiation in the microwave.

Not quite - that distance is exactly half the wavelength.

Sometimes when I watch tv and have a rubber band lying around, I like to play around with the strobing effect. This works best when you have a crt tv and slightly dim lighting. Stretching the band horizontal in front of the tv and twanging it can give nice standing waves. Streching it vertical gives distorted waves.
Great fun, but I'm easily amused.

I thought microwave ovens also contained a fan which dispersed the waves in a more-or-less random manner. If this is the case, areas which consistently miss out on the radiation may still occur, but these would not necessarily be distributed with any relation to the wavelength.

dragon wrote:I thought microwave ovens also contained a fan which dispersed the waves in a more-or-less random manner. If this is the case, areas which consistently miss out on the radiation may still occur, but these would not necessarily be distributed with any relation to the wavelength.

1. AFAIK, fans can't disperse EM waves.
2. There needs to be a standing wave pattern for heating to even occur.

FYI this will work with dry ice as well, for those interested, and is easier to obtain by those of us not near a university. My roomate and I did this in the back yard once and video'd it, it was impressive. A small 10oz water bottle exploded with enough force to cut a swath through the decidedly un-mown lawn. (we had the door shut)

Heres a simple lesson in density. Take a can of regular Coca Cola and a can of Diet, place them in a large enough tank of water. One will float, the other sink.
If you really want to bend brains, have a 2nd tank with a large amount of salt dissolved in it.

Also, and I just saw this the other day, here is "anti helium". Sulfur Hexaflouride gas, which is inert, but about 6 times denser than air.

Try inhaling SF6 as you would helium (in small, controlled, low-pressure amounts). Instead of making your voice squeaky, it makes it unnaturally deep. The squeaky He voice and the deep SF6 voice occur because your vocal chords produce sound by vibrating in one gas or the other and the sound produced travels at different speeds in each gas. By the time the sound reaches an observer's ears, it is in normal air and the speed has changed, thus altering the perceived frequency.

"Whenever you find yourself on the side of the majority, it is time to reform (or pause and reflect)."-- Mark Twain"There is not more dedicated criminal than a group of children."--addams

I've seen the sulfur hexaflouride demonstrations, they are pretty wild. My extent of home experiments reduces mostly to me and a buddy putting various things in the microwave. My favorite thing in the microwave is a lightbulb resting in a dixie cup which has just a LITTLE bit of water in the bottom, fun colors swirl around inside the bulb before it explodes.

Also, burning small pieces of wood (like the wood part of a match), so it's charred, then sticking these charred sticks upright in the wax of a candle close to but not touching the wick, lighting said wick on fire and then microwaving that is fun too the internet says that the fun colorful stuff that shoots out the top and swirls around the microwave ceiling is plasma, I'm not sure it I believe that it is actually matter in a plasma state. Does anyone know if the stuff is actually plasma?

Next on the list is filling a small dog dish (metal) with gasoline and microwaving that, his cousin just got a house out in the country so we can finally do it in a field in the middle of nowhere

My dad's a high school physics teacher with a fondness for home experiments, so we get plenty at my house. My personal favourites of everything we've done, in reverse awesome order, are:

3. Shave off the side of a penny with a file so that the zinc shows. Put it in a cup of acid. Eventually the acid will dissolve the zinc, leaving a hollow copper penny shell.

2. Take a lot of purple cabbage and a little water. Put them in a pot together. Cook the cabbage like that until most of the colour is diffused into the water. The less water you use, the more concentrated this will be. Take out the cabbage. Take some coffee filters. Cut them into strips, then soak part of the strips in the cabbage water and leave them to dry. Result: pH paper! (Optional: eat the cabbage. Personally I really like it.)

1. Despite the awesomeness of those two experiments, nothing has ever beaten the hovercraft in PURE AWESOME (well, there /was/ the five-foot-high model volcano...). But seriously, hovercraft was incredible. This site gives a better description of how to make one than I could, so: http://www.wikihow.com/Build-a-Riding-Hovercraft. My dad ended up duct taping a light lawn chair to the top, and my brother and I would ride it all over the house. Simple to make, fun to use!

I remember Mythbusters doing a thing on hovercraft and one of the guys made a machine similar to the one your link describes

I always get annoyed when they study myths that are obviously false upon inspection, like if jumping at the last second will save you if an elevator falls. Of course they just wanted to crash an elevator, and similar motives exist for other such myths, but still!

Using the paperclips as electrodes, you can electrolyse the water to hydrogen and oxygen inside the bottle. Mixing in baking soda with the water ensures that the resulting gas is trapped inside bubbles.

The baking soda (sodium bicarbonate) dissociates and is the electrolyte which allows the current to pass through the water (you could also use salt but then you get nasty chlorine gas). Then you can trap the resulting hydrogen gas in a container or you can add soap to the water to make the bubbles form automatically.

Also, burning small pieces of wood (like the wood part of a match), so it's charred, then sticking these charred sticks upright in the wax of a candle close to but not touching the wick, lighting said wick on fire and then microwaving that is fun too the internet says that the fun colorful stuff that shoots out the top and swirls around the microwave ceiling is plasma, I'm not sure it I believe that it is actually matter in a plasma state. Does anyone know if the stuff is actually plasma?

Plasma is a state of matter, so the difference between what they're saying and what you're thinking doesn't really exist.

Also, burning small pieces of wood (like the wood part of a match), so it's charred, then sticking these charred sticks upright in the wax of a candle close to but not touching the wick, lighting said wick on fire and then microwaving that is fun too the internet says that the fun colorful stuff that shoots out the top and swirls around the microwave ceiling is plasma, I'm not sure it I believe that it is actually matter in a plasma state. Does anyone know if the stuff is actually plasma?

Plasma is a state of matter, so the difference between what they're saying and what you're thinking doesn't really exist.

iirc a plasma is rather loosely defined compared to other phases of mater. i.e. not all ionised gases are necessarily plasma. that said it sounds like there is at least some plasma in that experiment even if there is also ionised gases

Also, burning small pieces of wood (like the wood part of a match), so it's charred, then sticking these charred sticks upright in the wax of a candle close to but not touching the wick, lighting said wick on fire and then microwaving that is fun too the internet says that the fun colorful stuff that shoots out the top and swirls around the microwave ceiling is plasma, I'm not sure it I believe that it is actually matter in a plasma state. Does anyone know if the stuff is actually plasma?

Plasma is a state of matter, so the difference between what they're saying and what you're thinking doesn't really exist.

But what he's asking is, is what he's seeing actually matter in a plasma state?

shill wrote:

dragon wrote:I thought microwave ovens also contained a fan which dispersed the waves in a more-or-less random manner. If this is the case, areas which consistently miss out on the radiation may still occur, but these would not necessarily be distributed with any relation to the wavelength.

1. AFAIK, fans can't disperse EM waves. 2. There needs to be a standing wave pattern for heating to even occur.

Normally I would agree, but wouldn't a spinning fan made of the right material be able to do this if the EM waves were 'shot' at it?

That's awesome. We tried this (without the awesomeness of the rocket, unfortunately) at my school one night and got about a 12 foot jet from a 2 liter and about 3 mentos. Eventually we ran out of other things to do with it so we started taking 20 oz bottles and trying to chug them right after spitting a mentos into it.

Totally not a hypothetical...

Steroid wrote:

bigglesworth wrote:If your economic reality is a choice, then why are you not as rich as Bill Gates?

evilbeanfiend wrote:iirc a plasma is rather loosely defined compared to other phases of mater. i.e. not all ionised gases are necessarily plasma. that said it sounds like there is at least some plasma in that experiment even if there is also ionised gases

Doesn't plasma also have to be super-heated? That's why I was doubtful. I have no trouble believing that a microwave could ionize something, but I can't see there being enough energy to superheat it....

I don't really know what I'm talking about or have any Chemistry intuition. A C+ In Chem101 is all the training I have.